ul{
    list-style: none;
    li{
        width: 300px;
        height: 30px;
        line-height: 30px;
        border: 1px solid #000;
        &:nth-child(2n){
            background:palevioletred;
        }
        &:nth-child(2n+1){
            background: greenyellow;
        }
        &:hover{
            background: #ccc;
        }
    }
}